Coolant Cooler With A Gearbox-Oil Cooler Integrated Into One Of The Cooling Water Reservoirs

ABSTRACT

The invention relates to a coolant cooler ( 7, 107 ) with a gearbox oil cooler ( 5, 105 ) which is integrated into one of the cooling water reservoirs ( 6, 106 ) of the coolant cooler ( 7, 107 ), wherein a second coolant inlet ( 13 ) and/or a second coolant angle ( 20 ) is/are provided on the coolant water reservoir ( 6, 106 ), enabling the circulation of coolant even when the motor thermostat ( 11 ) is closed.

The invention relates to a coolant cooler with a transmission oil cooler, which is integrated into one of the water reservoirs, for cooling transmission oil, according to the precharacterizing clause of claim 1.

FIG. 6 illustrates, according to the prior art, a coolant circuit 201 for cooling a refrigerant flowing through the engine 203, and a transmission oil circuit 202 for cooling a transmission oil flowing through a transmission 204. In this case, the transmission oil, owing to the increased heat input, is cooled by the colder coolant in the transmission oil cooler 205, which is arranged in a water reservoir 206 of the coolant cooler 207, the cooling power of the transmission oil cooler 205 being coupled to the flow through the coolant cooler 207. The flow directions of coolant and transmission oil are indicated by arrows. In the present case, an engine thermostat 211 is arranged on the coolant outlet side of the engine 203 and makes it possible, when the engine 203 is cold, for the coolant, by passing the coolant cooler 207, to pass directly via a bypass 213 to the pump 212 and back into the engine 203, i.e. coolant does not flow in the coolant cooler 207.

In the case of an arrangement of this type, during normal operation the transmission oil usually reaches transmission oil temperatures which are below the maximum value for continuous operation. At low coolant temperatures, which are below the opening temperature of the thermostat of the engine, the flow generally does not pass through the coolant cooler, and therefore cooling of the transmission is prevented. If there is a small leakage from the thermostat or at the beginning of the opening of the thermostat, the coolant passes through the coolant cooler at such a low rate that there is only a small cooling power available in the water reservoir for the transmission oil cooler, with the result that again excessive cooling of the transmission is prevented.

However, operating states may occur, in which the transmission generates very high amounts of waste heat, but the engine is not yet at its operating temperature, and so adequate cooling of the transmission oil cannot be ensured and there is the risk of the transmission overheating. This risk can be reduced by a fundamental leakage from the thermostat, but because of the associated, continuous heat output from the refrigerant cooler, the heating of the engine is delayed, and so the fuel consumption and pollutant emissions are increased and the heating comfort leaves something to be desired.

It is the object of the invention to provide an improved coolant cooler with a transmission oil cooler integrated into one of the water reservoirs, in accordance with which sufficient cooling of the transmission oil can be ensured even when the engine thermostat is closed. The coolant cooler is to be as cost-effective as possible.

This object is achieved by a heat exchanger with an additional heat exchanger, which is integrated in one of the collecting reservoirs, having the features of claim 1. Advantageous refinements are the subject matter of the subclaims.

The invention relates in particular to a coolant cooler with a transmission oil cooler integrated into one of the water reservoirs of the coolant cooler, wherein a second coolant inlet and/or a second coolant outlet is/are provided on the water reservoir, enabling the circulation of coolant even when the engine thermostat is closed, in particular when the engine is cold but the transmission oil is too hot. In this case, the transmission oil circuit preferably entirely corresponds to a conventional transmission oil circuit, and so no changes are required in this region, and the old components can continue to be used. Only on the water reservoir does a second coolant inlet and/or a second coolant outlet have to be provided, with the control preferably taking place via a thermostat, which can be integrated into the water reservoir or can be integrated in the coolant inlet or outlet. Apart from a bypass line to the second coolant inlet or outlet and a further branch line in the conventional coolant circuit, no changes are required, and it is possible for the branch line also to be integrated directly into the engine thermostat.

The second coolant inlet and/or the second coolant outlet is/are preferably arranged in the outlet water reservoir, in which the coolant temperature is below that of the coolant which comes from the engine and flows into the inlet water reservoir, thus making more effective cooling of the transmission oil possible because of the lower temperature. The inlet and/or outlet is/are preferably situated above the transmission oil cooler, since, in this upper region, when the flow is not passing through the coolant cooler, which is the case in particular when the engine is cold, the coolant temperature is higher than in the lower region of the water reservoir, since the hot coolant rises upward.

The thermostat preferably has an expansion element which projects into the water reservoir. With the aid of the expansion element, which expands at high temperatures and, in accordance with the arrangement of the same, opens a valve, the inlet or outlet can be controlled cost-effectively and in a simple manner.

In this case, in particular for inflowing coolant, a flow divider is arranged in the water reservoir, the flow divider separating a sensor region of the thermostat, that is, for example, the region in which an expansion element is arranged, in a region essentially free from coolant flow from the inflow region of the second coolant inlet.

Control of the flow through the water reservoir, in which the transmission oil cooler is arranged, as a function of the coolant temperature ensures that the transmission oil is adequately cooled and prevents overheating of the transmission oil, which, without appropriate control, could take place, in particular if the engine is not yet at its operating temperature and the transmission oil is too hot. The entire arrangement here is only insignificantly more expensive than a conventional arrangement with coolant circuit and transmission oil circuit.

According to a preferred embodiment, a valve closing the second coolant inlet and/or the second coolant outlet, in particular the thermostat, is activated from the outside, for example via electronics, and particularly preferably by heating. This makes it possible to actively heat the transmission oil in order, at low loads, to bring it more rapidly to the operating temperature and therefore to reduce friction losses. An opening of the valve at a coolant temperature somewhat below the temperature at which the engine thermostat opens is particularly advantageous.

This enables the transmission oil to be heated before the coolant cooler outputs heat to the surroundings.

The invention is explained in detail below using two exemplary embodiments and with reference to the drawing, in which:

FIG. 1 shows a schematic illustration of a coolant circuit and of a transmission oil circuit according to the first exemplary embodiment,

FIG. 2 shows a schematic side view of the outlet water reservoir with transmission oil cooler according to the first exemplary embodiment,

FIG. 3 shows a schematic detail illustration of the upper region of the outlet water reservoir of FIG. 2,

FIG. 4 shows a schematic illustration of a coolant circuit and of a transmission oil circuit according to the second exemplary embodiment,

FIG. 5 shows a schematic detail illustration of the upper region of the outlet water reservoir according to the second exemplary embodiment, and

FIG. 6 shows a schematic illustration of a coolant circuit and of a transmission oil circuit according to the prior art.

FIG. 1 shows a coolant circuit 1 and a transmission oil circuit 2 of a transmission 4, which is connected to an engine 3 and has an infinitely variable transmission ratio, according to the first exemplary embodiment. In this case—in accordance with the prior art—in order to cool the transmission oil a transmission oil cooler 5 is arranged in a water reservoir 6, in the present case the outlet water reservoir 6′, of a coolant cooler 7. The transmission oil circuit 2 corresponds here to the transmission oil circuit 102 according to the previously described prior art, and so it is not discussed in more detail.

During normal operation—in accordance with conventional coolant circuits—the coolant coming from the engine 3 flows via a line 8 to the coolant cooler 7, which it leaves at the coolant outlet connection piece 9, and via a line 10 to an engine thermostat 11 and via a coolant pump 12 back to the engine 3. If the coolant is adequately cool, for example during starting of the engine 3, then the engine thermostat 11 blocks the line 10, and the coolant passes via a bypass 13 directly from the engine 3 to the engine thermostat 11 and the pump 12 arranged downstream thereof. To this extent, the coolant circuit 1 corresponds to a conventional coolant circuit.

In addition, in order to ensure adequate cooling of the transmission oil when the engine thermostat 11 is closed with regard to the line 10, a second coolant outlet 20 is provided on the outlet water reservoir 6′ of the coolant cooler 7, in which reservoir the transmission oil cooler 5 is arranged, said second coolant outlet being controlled by a second thermostat 21, and from which the coolant can be supplied via a bypass line 22 directly to the bypass 13. In this case, the thermostat 21 determines the temperature of the coolant, which is convectively heated in the water reservoir 6 by the hot transmission oil flowing through the transmission oil cooler 5. In the present case, the thermostat 21 is mounted directly on the water reservoir 6, but it may also be integrated into a second coolant outlet connection piece. Since the hot coolant rises upward in the water reservoir 6, the second thermostat 21 is provided at the top, above the transmission oil cooler 5.

In order for a flow to form through the bypass line 22, a sufficient drop of pressure is required. When the engine temperature is controlled via an engine thermostat 11 at the inlet of the engine, as illustrated in FIG. 1, the heated coolant passes the engine thermostat 11 via the bypass 13, with the result that there is a sufficient drop of pressure even when the engine thermostat 11 is closed, and flow is therefore possible.

According to a variant which is not illustrated in the drawing, the bypass line 22 leads to an additional connection piece directly into the housing of the engine thermostat, the connection piece being arranged in such a manner that it opens into the engine return behind the actual valve.

At low coolant temperatures, it can therefore be ensured that—when the coolant is at a relatively high temperature in the region of the transmission oil cooler 5—the operation of the transmission oil cooler 5 can be guaranteed by adequate flow passing through the outlet water reservoir 6′.

In the present case, a thermostat with an expansion element 23 is used as the second thermostat 21, the expansion element 23 projecting into the water reservoir 6. Heating the expansion element 23 causes the thermostat valve 24, of which the valve seat 25 and valve disk 26 are indicated in FIG. 3, to open up the flow path through the second outlet connection piece 27 via the bypass line 22. The convection is indicated in FIG. 3 by an arrow (not filled in) above the transmission oil cooler 5.

In the following text, the second exemplary embodiment is explained in more detail with reference to FIGS. 4 and 5. In this case, identical elements or elements acting to like effect are referred to by reference numbers higher by 100 than in the first exemplary embodiment.

In this case, a coolant circuit 101 and a transmission oil circuit 102 are again provided, with the transmission oil circuit 102 corresponding here to the transmission oil circuit 2 and to the transmission oil circuit 202 according to the previously described exemplary embodiment and the prior art, and so it is not discussed in more detail.

A transmission 104 connected to an engine 103, in the present case an automatic transmission with a converter clutch, is cooled by the transmission oil, which flows through the transmission oil circuit 102 and, in a transmission oil cooler 105, which is arranged in a water reservoir 106, in the present case again the outlet water reservoir 106′, of a coolant cooler 107, outputs the absorbed heat to the coolant which circulates in the coolant circuit 101.

In contrast to the first exemplary embodiment, the engine thermostat 111 is arranged in the coolant circuit 101 on the engine outlet side. During normal operation, the coolant coming from the engine 103 flows through the engine thermostat 111 via a line 108 to the coolant cooler 107, which it leaves at a coolant outlet connection piece 109, and via a line 110 to a coolant pump 112 and back to the engine 103.

If the coolant is sufficiently cool, for example during starting of the engine 103, then the engine thermostat 111 blocks the line 108, and the coolant passes via a bypass 113 from the engine 103 directly to the line 110 and to the pump 112. To this extent, the coolant circuit 1 again corresponds to a conventional coolant circuit, in the present case to the coolant circuit 201 (illustrated in FIG. 6) according to the prior art.

In addition, in order to ensure adequate cooling of the transmission oil when the engine thermostat 111 is closed with respect to the line 108, instead of the second coolant outlet 20 according to the first exemplary embodiment, a second coolant inlet 130 is provided on the outlet water reservoir 106′ of the coolant cooler 107, in which reservoir the transmission oil cooler 105 is arranged, which second coolant inlet is controlled by a second thermostat 131. In this case, if the need arises, coolant can pass via a bypass line 132 from the engine thermostat 111 to the second thermostat 131 and into the water reservoir 106. From the water reservoir 106, the coolant, after it has absorbed heat from the transmission oil cooler 105, passes in a customary manner via the coolant outlet connection piece 109 and via the line 110 to the pump 112 and back into the engine 103. In the present case, the bypass line 132 is integrated into the housing of the engine thermostat 111 in such a manner that it is closed when the engine thermostat 111 is open, and so no coolant passes via the bypass line 132 into the water reservoir 106, but rather all of the coolant takes the normal flow path via the line 108 to the coolant cooler 107 and enters the latter via the inlet water reservoir 106′.

In this case, in accordance with the thermostat 21 of the first exemplary embodiment, the thermostat 131 determines the temperature of the coolant, which is convectively heated in the water reservoir 106 by the hot transmission oil flowing through the transmission oil cooler 105. The thermostat 131 is fitted directly in the water reservoir 106 (cf. FIG. 5), but it may also be integrated into a second coolant inlet connection piece. Since the hot coolant rises upward in the water reservoir 106, the second thermostat 131 is fitted, in accordance with the thermostat 21 of the first exemplary embodiment, at the top, above the transmission oil cooler 105, but, in the present case, the configuration of the thermostat 131 differs from that of the thermostat 21.

The expansion element of the thermostat 131 is arranged here on a wall of the water reservoir 106, which wall lies opposite the valve with valve seat and valve disk, with a flow divider in the form of a partition being arranged in between, so that if the engine 103 is not at its operating temperature, cool coolant does not come into contact with the expansion element and thus closes the thermostat again, although a flow is desired.

The second thermostat 131 again has an expansion element 133 and a thermostat valve 134 with a valve seat 135 and valve disk 136, which are arranged on a second inlet connection piece 137. However, the expansion element 133, which is arranged above the transmission oil cooler 105 on one side of the water reservoir 106 and forms a sensor region of the thermostat 131, and the thermostat valve 134, which is arranged above the transmission oil cooler 105 on the opposite side of the water reservoir 106, are separated by a flow divider 138, which is formed by a wall projecting in the direction of the transmission oil cooler 105, said flow divider preventing, when the thermostat valve 134 is open, a flow which cools the expansion element 133 being formed in the region thereof instead of the flow as a result of the heat convection, and so unintentional closing of the second thermostat 131 is prevented.

LIST OF REFERENCE NUMBERS

-   1, 101, 201 Coolant circuit -   2, 102, 202 Transmission oil circuit -   3, 103, 203 Engine -   4, 104, 204 Transmission -   5, 105, 205 Transmission oil cooler -   6, 106, 206 Water reservoir -   6′, 106′ Outlet water reservoir -   6″, 106″ Inlet water reservoir -   7, 107, 207 Coolant cooler -   8, 108 Line -   9, 109 Coolant outlet connection piece -   10, 110 Line -   11, 111, 211 Engine thermostat -   12, 112, 212 Coolant pump -   13, 213 Bypass -   20 Second coolant outlet -   21 Second thermostat -   22 Bypass line -   23 Expansion element -   24 Thermostat valve -   25 Valve seat -   26 Valve disk -   27 Second outlet connection piece -   130 Second coolant inlet -   131 Second thermostat -   132 Bypass line -   133 Expansion element -   134 Thermostat valve -   135 Valve seat -   136 Valve disk -   137 Second inlet connection piece -   138 Flow divider 

1. A heat exchanger, in particular coolant cooler with an additional heat exchanger, in particular transmission oil cooler, integrated into one of the collecting or water reservoirs of the heat exchanger or coolant cooler wherein a second coolant inlet and/or a second coolant outlet is/are provided on the collecting or water reservoir.
 2. The coolant cooler as claimed in claim 1, wherein the second coolant inlet and/or the second coolant outlet can be closed in a controlled manner by a thermostat.
 3. The coolant cooler as claimed in claim 1, wherein the second coolant inlet and/or the second coolant outlet is/are connected to a bypass line which branches off from an engine thermostat or leads to an engine thermostat.
 4. The coolant cooler as claimed in claim 1, wherein the second coolant inlet and/or the second coolant outlet is/are arranged in the outlet water reservoir.
 5. The coolant cooler as claimed in claim 1, wherein the second coolant inlet and/or the second coolant outlet is/are arranged above the transmission oil cooler.
 6. The coolant cooler as claimed in claim 2, wherein the thermostat has an expansion element which projects into the water reservoir.
 7. The coolant cooler as claimed in claim 1, wherein a flow divider is arranged in the water reservoir the flow divider separating a sensor region of the thermostat in a region essentially free from coolant flow from the inflow region of the second coolant inlet.
 8. The coolant cooler as claimed in claim 1, wherein the second coolant inlet and/or the second coolant outlet can be closed in a controlled manner by an, in particular, electronically controllable valve.
 9. The coolant cooler as claimed in claim 8, wherein the valve is a thermostat, in particular with an expansion element, which, in particular, has a heating system for controlling the thermostat.
 10. A method for controlling a coolant cooler as claimed in claim 1, wherein the second coolant inlet and/or the second coolant outlet is/are controlled by a thermostat as a function of the coolant temperature.
 11. The method as claimed in claim 10, wherein the second coolant inlet and/or the second coolant outlet is/are opened when the engine is not yet at its operating temperature and the transmission oil is too hot.
 12. The method as claimed in claim 1, wherein the second coolant inlet and/or the second coolant outlet is/are opened when the engine is, in particular, not yet at its operating temperature and the transmission oil is not yet at its operating temperature.
 13. The method as claimed in claim 1, wherein opening the second coolant inlet and/or the second coolant outlet is predetermined from the outside, in particular by heating a thermostat closing the opening. 